1. Field of the Invention
The disclosures herein generally relate to a physical distribution management system and a physical distribution management method in which a conveyance container is placed on a conveyance unit and is conveyed, and in particular relates to a physical distribution management system and a physical distribution management method in which an error in an input sequence (in the following, called an “error in category input sequence”) of plural kinds of conveyance containers mixed on the conveyance unit can be detected.
2. Description of the Related Art
On some plastic containers as conveyance containers used in a factory, for example, heat sensitive type labels, on which destinations of articles held in the containers or names of the articles are printed, are applied. These labels have a property of turning colors by heat, and it is possible to write a character or a symbol onto the labels by using a thermal head or the like.
Moreover, rewritable type heat sensitive papers are used for the above described container labels, on which write/erase operations can be repeated. In order to use such labels for physical distributions, it is desirable that the write/erase operations on the labels can be performed while being attached to containers. For that purpose, for example, Japanese Published Patent Application No. 2004-90026 discloses an information writing device called a laser marker, which emits laser light on the label contactlessly to heat it, thereby writing a character or the like.
The above-described laser marker may be used for printing destinations of articles or names of articles in a process of conveying and sorting the articles in a factory, a distribution center or the like. Specifically, heat sensitive type labels are applied to surfaces on containers serially conveyed by a conveyer as a conveyance device in the factory, and printing is performed on each of the heat sensitive type labels.
Print information to be written on the heat sensitive type label includes information which is fixed within an arbitrary period and information which is different for each of the objects for writing.
The above-described information may be managed on the side of the writing device such as the laser marker, but generally the above information is managed and controlled by a personal computer, which may be denoted as a host PC or a higher level device, connected to the writing device such as the laser marker via a communication mechanism.
In a conveyance system installed in the above described distribution center or the like, plural kinds of containers to be input into the conveyer may be mixed. For example, regarding the size of a container (outer size, inner size, volume or capacity), when a size of an article held in a container is small, a small-sized container is used. When the size of the article held in a container is large, a large-sized container is used. In this way, by using plural kinds of containers having a size according to the content, a space of a conveyance vehicle in the final stage of the conveyance can be used effectively.
In the above-described conveyance system in which containers having different sizes are mixed, an error in the input sequence of the containers may occur. Since a size of container generally corresponds to an article held in the container, the size of the container input to the conveyer is also managed by the conveyance system. However, the process of inputting the container into the conveyer is performed manually in general, and there may be a risk of inputting a container having a size different from the size instructed by the system. In the specification of the present application, the above described error will be denoted as “error in input sequence by size”
When the error in input sequence by size occurs and a container is conveyed to a process of storing an article in the container, which will be called “article storage process”, without detecting the error, a serious problem may occur. That is, when a small container is input at a timing of inputting a large container, a trouble that an article to be stored cannot be stored in the container occurs in the stage of storing the article in the container.
In the above case, it may not be recovered from the trouble by merely re-inputting a container. Depending on the configuration of the conveyance system, all containers input after the container which has generated the error in an input sequence may need to be re-input. Accordingly, it is an important object to detect the error in input sequence by size early.
Japanese Published Patent Application No. 2003-300606 discloses a picking system that can detect an error in input sequence of containers input to a conveyer. In the picking system, information recording media applied to containers are issued, wherein identification information for identifying the container is recorded on the information recording medium, the container identification information is sent to an operation zone on the conveyance path in the sequence that the information recording media are issued. The container identification information applied to the container is read out in each operation zone, and it is determined whether the readout container identification information is the same sequence as the issued identification information, thereby detecting the error in input sequence.
However, in the picking system disclosed in Japanese Published Patent Application No. 2003-300606, a size or a shape of a container is not taken into account, and an error in input sequence by type, such as an error in input sequence by size or an error in input sequence by shape, cannot be detected.